This invention concerns novel thermoset paint compositions. More precisely, the invention concerns thermoset paint compositions which are useful as top coat paints for automobile purposes which have excellent acid resistance, abrasion resistance, adhesion, staining resistance and water repelling properties.
In past years, the problem of paint film durability, especially rain spotting due to acid rain and abrasion due to rotating car-wash brushes and the sand and dust which is thrown up while driving, has arisen. Various means of providing improvements in respect of this problem have been suggested. For example, top coat paints which have excellent abrasion resistance and which contain alkoxymonomeric melamine resin, acrylic resin which has an open ring lactone chain, and fluorine containing resin, have been disclosed in Japanese Patent Kokai H3-288577. However, although a paint film which has excellent abrasion resistance is obtained with this technology, the bonds which are formed by the reaction of the alkoxy groups of the melamine resin and the polyol hydroxy groups are readily hydrolyzed by acids and so it is difficult to achieve good acid resisting performance. Furthermore, it is known that the alkoxy groups in a melamine resin form crosslinks quantitatively with hydroxy groups, and the effective crosslink density is dominated by the hydroxy group content. Consequently, in those cases where there are mol equivalents of hydroxy group and melamine resin alkoxy group, or where the alkoxy group is in excess, attachment to the base coat of a two-coat one-bake painting type paint film is poor and, moreover, recoat adhesion failure of a recoat painting paint film which has been obtained by means of the same painting process on a two-coat one-bake painting paint film can occur.
Paint compositions which have excellent abrasion resistance which include a fluorine containing copolymer, comprising hydroxy group containing long chain vinyl ether represented by the formula CH2xe2x95x90CHO(CH2)nOH (where n is 7 to 18) and fluoro-olefin, and a hardener which has functional groups which react with hydroxy groups, have been proposed in Japanese Patent Kokai H5-105840. Furthermore, catalyst free paint compositions which include copolymers obtained by reacting fluorine containing copolymers and polybasic acid anhydrides, and alkyl etherified melamine resin and isocyanate compound or blocked isocyanate compound, have been disclosed in Japanese Patent Kokai 61-200145.
However, although the abrasion resistance is certainly improved with the former technique, the acid resistance is unsatisfactory. Furthermore, although a paint film which has excellent acid resistance is obtained with the latter technique, the abrasion resistance is unsatisfactory. Moreover, although paint films which have excellent weather resistance and resistance to chemical attack are certainly obtained with these techniques because of the use of a fluorine resin, the glass transition temperature of the paint films obtained is not controlled and so, in those cases where the glass transition temperature is low, the molecular structure of the paint film is liable to be dominated by the external environment, the movement of atoms or molecules is facilitated, and this causes orientation of polar groups or non-polar groups at the paint film surface. Consequently, the water repelling properties and staining resistance which are the distinguishing features of a fluorine resin are not realized satisfactorily, and with such external physical and chemical changes it is difficult to maintain satisfactorily the features of the fluorine resin.
The aim of this present invention is to provide thermoset paint compositions which resolve the problems of the conventional fluorine resin based paint films such as those described above, which can form paint films which have excellent acid resistance and abrasion resistance, and which also have excellent adhesion properties, staining resistance and water repelling properties.
As a result of thorough research carried out with a view to achieving the abovementioned aim, the inventors have discovered that the abovementioned aim can be achieved by means of blocked isocyanate compound, alkyl etherified melamine resin, (co)polymer which has terminal hydroxy groups at a position removed from the main chain and of which the solubility parameter and the hydroxy group value are within specified ranges, and fluorine containing copolymer of which the solubility parameter and the hydroxy group value are within specified ranges, and by providing material such that the glass transition temperature of the paint film after hardening is at least 50xc2x0 C., and the invention is based upon this discovery.
That is to say, the present invention is a thermoset paint composition as indicated below.
(1) Thermoset paint composition, characterized in that it contains:
(a) from 20 to 80% by weight of fluorine containing copolymer, being a copolymer of fluoro-olefin, hydroxy group containing vinyl based monomer and other vinyl based monomer, of which the solubility parameter is from 9.0 to 10.5 and the hydroxy group value is within the range from 60 to 150 mgKOH/g.
(b) from 20-80% by weight of vinyl based (co)polymer, being a (co)polymer comprising vinyl based monomer which contains at least 10% by weight of monomer which can be represented by the general formula [1] indicated below, of which the solubility parameter is from 9.0 to 10.5 and the hydroxy group value is within the range from 60 to 150 mgKOH/g,
(c) from 5 to 40% by weight of alkyl etherified melamine resin, and
(d) from 2 to 40% by weight of blocked polyisocyanate compound, and in that the glass transition temperature of the paint film after hardening is at least 50xc2x0 C. General Formula [1]
(R1 to R5 each independently represent H or methyl group, i is 0-2, j is 0 or 1. k is 0-3, m is 0-3 and n is 0-10.)
(2) Thermoset paint composition, according to (1) above, wherein the fluorine containing copolymer (a) contains at least 10% by weight of hydroxy group containing vinyl based monomer which has at least four elements between the vinyl group and the hydroxy group, and in which the hydroxy group is located terminally.
A hardened paint film obtained by means of the thermoset paint compositions of this invention has a high glass transition temperature and, since a fluorine containing copolymer (a) is used as a main resin and a combination in which blocked polyisocyanate compound (d) which can form urethane bonds which have excellent resistance to chemical attack is used conjointly as well as the alkyl etherified melamine resin (c) for the hardener, the permeability of the paint film to hydrophilic substances such as acid rain is low, and it has a stable paint film structure which is not liable to bonding failure with acidic materials. Because of its excellent acid resistance and staining resistance, its water repelling properties can be retained over a longer time than with the conventional fluorine based paint films. Moreover, the crosslink structure which the soft segments which have hydroxy groups at the ends of flexible atomic groups which are located remote from the main chain of the vinyl based (co)polymer (b) can form, and the cohesive force of the urethane bonds which the blocked polyisocyanate compound (d) can form, impart elasticity such that the paint film recovers properly and is not deformed and/or ruptured by a load resulting from rubbing the paint film, and paint films which have excellent abrasion resistance can be formed. Moreover, the paint compositions of this invention also have excellent flex resistance and adhesion on recoating.
Tetrafluoroethylene, chlorotrifluoroethylene, 1,1-difluoroethylene, hexafluoropropylene, vinyl fluoride, vinylidene fluoride and derivatives such as carboxylic acid containing fluoro-olefins, for example, can be used as the fluoro-olefin copolymer component of the fluorine containing copolymer (a) which is used in this invention. These may be used individually, or two or more types may be used in combination.
The amount of fluoro-olefin included in the fluorine containing copolymer (a) can be varied arbitrarily, but it is, preferably from 20 to 60% by weight. If the amount exceeds 60% by weight then the solubility of the fluorine containing copolymer (a) in organic solvent is reduced, and if it is less than 20% by weight then the properties, such as the weather resistance and resistance to chemical attack, are adversely affected, and the water repelling properties and staining resistance which are characteristic of a fluorine based paint film are not realized.
The use of vinyl based monomers which have at least four elements between the vinyl group and the hydroxy group and in which the hydroxy group is located terminally are preferred for the hydroxy group containing vinyl based monomer copolymer component of the fluorine containing copolymer (a). Actual examples of such hydroxy group containing vinyl based monomers include hydroxy group containing vinyl ethers such as hydroxypropyl vinyl ether, hydroxybutyl vinyl ether and hydroxyhexyl vinyl ether; hydroxy group containing allyl ethers such as 2-allyloxy-1-ethanol, 3-allyloxy-1-propanol, 4-allyloxy-1-butanol, 5-allyloxy-1-pentanol, 6-allyloxy-1-hexanol, 7-allyloxy-1-heptanol, 8-allyloxy-1-octanol, the mono-allyl nether of polyethyleneglycol and the mono-allyl ether of polypropyleneglycol; mono-ethers of hydroxy group containing vinyl based monomers, such as 2-hydroxy (meth)acrylate or 2-hydroxypropyl (meth)acrylate, with polyether polyols such as polyethyleneglycol, polypropyleneglycol and polybutyleneglycol; monoesters or diesters of glycols such as polyethyleneglycol, polypropyleneglycol and 1,6-hexanediol with acid anhydride group containing vinyl based monomers, such as maleic acid anhydride and itaconic acid anhydride, and lactone modified vinyl based monomers wherein from 0 to 10 mol of lactone, such as xcex5-caprolactone, xcex2-methyl-xcex4-valerolactone, "khgr"-valerolactone, xcex4-valerolactone, xcex1-caprolactone, xcex5-caprolactone, xcex2-propiolactone or "khgr"-butyrolactone for example, had been added to a hydroxy group containing vinyl monomer, such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate or hydroxybutyl (meth)acrylate for example.
When a vinyl monomer which has soft segments in which there are at least four elements between the vinyl group and the hydroxy group and in which the hydroxy group is located terminally is used for the hydroxy group containing vinyl based monomer which is a copolymer component of the fluorine containing resin (a), it is possible to impart elastic strength to the paint film obtained, and so it is possible to form paint films which are elastic and have excellent abrasion resistance.
The amount of hydroxy group containing vinyl based monomer included in the (a) component is preferably at least 10% by weight, and most desirably from 15 to 70% by weight. In those cases where the hydroxy group containing vinyl based monomer content is less than 10% by weight and in those cases where there are fewer than four elements between the vinyl group and the hydroxy group it is impossible to impart satisfactory elastic strength to the paint film obtained, and the abrasion resistance is unsatisfactory. Furthermore, in those cases where the hydroxy group is located other than terminally, the reactivity of the hydroxy group is reduced, and satisfactory adhesion is not obtained.
Examples of the other vinyl based monomer copolymer components of the fluorine based copolymer (a) include the C1-C18 alkyl or cycloalkyl esters of (meth)acrylic acid, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate and cyclohexyl (meth)acrylate; and also 2-hydroxyethyl (meth)acrylate, styrene, styrene derivatives, acrylonitrile, acrylamide, vinyltoluene, vinyl acetate, vinyl propionate, glycidyl (meth)acrylate, (meth)acrylic acid, ethyl vinyl ether, isobutyl vinyl ether, n-butyl vinyl ether, cyclohexyl vinyl ether and such like compounds. These may be used individually, or they may be used in combinations of two or more types.
The fluorine containing copolymer (a) component comprises fluoro-olefin, hydroxy group containing vinyl based monomer and other vinyl based monomer, as described above, but it may be modified by adding carboxylic acid to the resin using a triethylbenzylammonium chloride, for example, as catalyst, to add an acid anhydride, such as succinic anhydride, to the hydroxy groups in the molecule, as required.
The solubility parameter of the fluorine containing copolymer component (a) used in the invention is within the range from 9.0 to 10.5, and preferably within the range from 9.2 to 10.3. In those cases where the solubility parameter exceeds 10.5 the polarity of the fluorine based copolymer (a) is high and it becomes difficult to obtain a smooth paint film surface, and this is undesirable since the appearance of the paint film is adversely affected. Moreover, it is liable to cause a worsening of the water repelling properties and the staining resistance. Conversely, in those cases where the solubility parameter is less than 9.0, the compatibility with the (b) component, the (c) component and the (d) component is reduced, and this is undesirable.
Moreover, the solubility parameter can be measured in the following way. Thus, it can be obtained from the arithmetic average (SPH+SPW)/2 of the acetone/hexane mixed solubility parameter (SPH) observed when 1 gram of resin solid fraction is diluted 50 times with acetone and then n-hexane is added gradually to the dilute solution which is obtained until the resin solution becomes turbid and the acetone/water mixed liquid solubility parameter (SPW) observed when 1 gram resin solid fraction is diluted 50 times with acetone and then distilled water is added gradually to the dilute solution which is obtained until the resin solution becomes turbid. The solubility parameter indicates a resin of higher polarity as the value becomes larger and a resin of lower polarity as the value becomes lower.
Furthermore, the (a) component fluorine containing copolymer has a hydroxy group value within the range from 60 to 150 mgKOH/g, and preferably within the range from 70 to 140 mgKOH/g. In those cases where the hydroxy group value exceeds 150 mgKOH/g the solubility in solvent is decreased and, moreover, the appearance of the paint film is liable to be adversely affected, and this is undesirable. Conversely, in those cases where it is less than 60 mgKOH/g a satisfactory crosslink density for a hardened paint film cannot be obtained and the mechanical strength and solvent resistance of the paint film are unsatisfactory, and this is undesirable.
The (a) component fluorine containing copolymer can be obtained by means of a copolymerization reaction using a known method, such as solution polymerization, emulsion polymerization, suspension polymerization or bulk polymerization, in the presence of the usual radical initiators in an autoclave using a mixture of the aforementioned monomers.
Furthermore, commercial products can be used for the fluorine containing copolymer (a). Actual examples of such products include xe2x80x9cRumifronxe2x80x9d [trade name, manufactured the Asahi Garasu Co.], xe2x80x9cFluonatexe2x80x9d [trade name, manufactured by the Dainippon Inki Kagaku Kogyo Co.], xe2x80x9cSefralcoatxe2x80x9d [trade name, manufactured by the Sentoraru Garasu Co.], xe2x80x9cZaflonxe2x80x9d [trade name, manufactured by the Toa Gosei Kagaku Kogyo Co.] and xe2x80x9cZeffruxe2x80x9d [trade name, manufactured by the Daikin Kogyo Co.].
Monomers which can be represented by general formula [1] which are (co)polymer components of the vinyl based (co)polymer (b) which is used in the invention include, for example, the mono-ethers of hydroxy group containing vinyl based monomers such as 2-hydroxyethyl (meth)acrylate or 2-hydroxypropyl (meth)acrylate with polyether polyols such as polyethyleneglycol, polypropyleneglycol and polybutylene glycol; monoesters or diesters of glycols such as polyethyleneglycol, polypropyleneglycol, 1,4-butanediol and 1,6-hexanediol with acid anhydride group containing vinyl based monomers such as maleic acid anhydride and itaconic acid anhydride; and lactone modified vinyl based monomers wherein from 0 to 10 mol of lactone, such as xcex5-caprolactone, xcex2-methyl-xcex4-valerolactone, "khgr"-valerolactone, xcex4-valerolactone, xcex1-caprolactone, xcex5-caprolactone, xcex2-propiolactone or "khgr"-butyrolactone for example, has been added to a hydroxy group containing vinyl monomer such as 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate or hydroxybutyl (meth)acrylate for example. These may be used individually, or two or more types can be used in combination.
Furthermore, vinyl monomers which do not contain fluorine can be used for the other vinyl based monomer which is a copolymer component of the vinyl based (co)polymer (b), and examples of these monomers include the C1-C18 alkyl or cycloalkyl esters of (meth)acrylic acid, such as methyl (meth)acrylate, ethyl (meth)acrylate, propyl (meth)acrylate, n-butyl (meth)acrylate, isobutyl (meth)acrylate, t-butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, n-octyl (meth)acrylate, lauryl (meth)acrylate, tridecyl (meth)acrylate, stearyl (meth)acrylate and cyclohexyl (meth)acrylate; and also 2-hydroxyethyl (meth)acrylate, styrene, styrene derivatives, acrylonitrile, acrylamide, vinyltoluene, vinyl acetate, vinyl propionate, glycidyl (meth)acrylate, (meth)acrylic acid and such like compounds. These may be used individually, or they may be used in combinations of two or more types.
The monomer represented by general formula [1] which is a (co)polymer component of the vinyl based (co)polymer (b) has a soft segment such that there are at least 4 elements between the vinyl group, and the hydroxy group and the hydroxy group is located terminally, and so the paint film obtained has elastic strength and can exhibit excellent abrasion resistance.
The amount of the aforementioned monomer represented by general formula [1] in the vinyl based (co)polymer (b) must be at least 10% by weight, but the inclusion of from 15 to 70% by weight is preferred. If the amount included is less than 10% by weight then it is impossible to provide the paint film with sufficient elastic strength, and not only is the abrasion resistance reduced but the flex resistance of the paint film obtained and the adhesion on recoating are adversely affected as well, and the aim of the invention is not realized.
The solubility parameter of the vinyl based (co)polymer (b) component used in the invention is within the range from 9.0 to 10.5, and preferably within the range from 9.2 to 10.3. In those cases where the solubility parameter exceeds 10.5 the polarity of the vinyl based (co)polymer (b) is high and it becomes difficult to obtain a smooth paint film surface, and this is undesirable since the appearance of the paint film is adversely affected. Conversely, in those cases where the solubility parameter is less than 9.0 the compatibility with the (a) component, the (c) component and the (d) component is reduced, and this is undesirable. The solubility parameter can be obtained in the same way as before.
Furthermore, the (b) component vinyl based (co)polymer has a hydroxy group value within the range from 60 to 150 mgKOH/g, and preferably within the range from 70 to 140 mgKOH/g. In those cases where the hydroxy group value exceeds 150 mgKOH/g the solubility in solvent is decreased and, moreover, the appearance of the paint film is liable to be adversely affected, and this is undesirable. Conversely, in those cases where it is less than 60 mgKOH/g a satisfactory crosslink density for a hardened paint film cannot be obtained and the mechanical strength and solvent resistance of the paint film are unsatisfactory, and this is undesirable.
The component (b) vinyl based (co)polymer can be obtained by carrying out a (co)polymerization reaction in the usual way, using the aforementioned monomer represented by general formula [1], or a vinyl based monomer mixture which contains the aforementioned monomer represented by general formula [1] and other vinyl monomer in the aforementioned proportions, in the presence of a known polymerization initiator, such as azobisisobutyronitrile, benzoyl peroxide, t-butylperoxy benzoate, t-butyl hydroperoxide, t-butylperoxy octoate, di-t-butyl peroxide or cumene hydroperoxide for example.
The alkyl etherified melamine resins normally used as hardeners in the paint field can be used for the alkyl etherified melamine resin (c) component which is used in this invention, but those obtained by methylolation of aminotriazine and alkyletherification with cyclohexanol or alkanols which have from 1 to 6 carbon atoms are preferred. Actual examples include butyl etherified melamine, methyl etherified melamine resin and mixed butyl/methyl etherified melamine resin. Actual examples of butyl etherified melamine resin include xe2x80x9cYuban 20SExe2x80x9d [trade name, manufactured by the Mitsui Toatsu Kagaku Co.] and xe2x80x9cSuperbekkamin L-116-70xe2x80x9d [trade name, manufactured by the Dainippon Inki Kagaku Kogyo Co.]; and actual examples of methyl etherified melamine resin and mixed butyl/ethyl etherified melamine resin include xe2x80x9cNikalac MS-11xe2x80x9d [trade name, manufactured by the Sanwa Chemical Co.] and xe2x80x9cSaimel 235xe2x80x9d [trade name, manufactured by the Mitsui Saitekku Co.].
The blocked products of the polyisocyanate compounds normally used as hardeners in the paint field can be used for the blocked polyisocyanate compound component (d) which is used in the invention and, for example, aromatic compounds, aliphatic compounds and non-yellowing type compounds can all be used. Actual examples of non-yellowing type blocked polyisocyanate compounds include those in which a polyisocyanate compound such as hexamethylene diisocyanate, trimethyl-hexamethylene diisocyanate, isophorone diisocyanate, hydrogenated diphenylmethane diisocyanate or hydrogenated xylylene diisocyanate or their adducts, biuret forms or isocyanurate forms has been blocked with the usual isocyanate blocking agents, including phenols, such as phenol, m-cresol, xylenol and thiophenol for example, alcohols, such as methanol, ethanol, butanol, 2-ethylhexanol and cyclohexanol for example, or active hydrogen containing compounds, such as caprolactam, methyl ethyl ketone oxime, ethyl acetoacetate and diethyl malonate for example. Actual examples of the blocked polyisocyanate compounds (d) include xe2x80x9cDesmodure BL-3175xe2x80x9d [trade name, manufactured by the Sumitomo Bayer Urethane Co.], xe2x80x9cCoronate 2513xe2x80x9d [trade name, manufactured by the Nippon Polyurethane Kogyo Co.], xe2x80x9cDuranate 17B-60PXxe2x80x9d [trade name, manufactured by the Asahi Kasei Kogyo Co.] and xe2x80x9cTakenate XB-72-G16xe2x80x9d [trade name, manufactured by the Takeda Yakuhin Kogyo Co.).
The compounding proportions of each resin component used in a thermoset paint composition of this invention must be in the range, on the basis of the total weight of the resin components (a) to (d), from 20 to 80% by weight, and preferably from 20 to 70% by weight, of component (a), from 20 to 80% by weight, and preferably from 20 to 70% by weight, of component (b), from 5 to 40% by weight, and preferably from 5 to 30% by weight, of component (c) and from 2 to 40% by weight, and preferably from 5 to 30% by weight, of component (d). If the (a) component content is less than 20% by weight then the properties of the fluorine containing copolymer (a) are not realized satisfactorily and the water repelling properties and the staining resistance of the paint film obtained are reduced, and if the amount included exceeds 80% by weight then the amount of hardener is insufficient and the formation of the crosslink structure in the paint film obtained is unsatisfactory, and the solvent resistance is reduced. Furthermore, if the (b) component content is less than 20% by weight then it is not possible to impart sufficient elastic strength to the paint film obtained and the abrasion resistance is unsatisfactory, or adhesion on recoating is reduced. On the other hand, if the amount exceeds 80% by weight then there is insufficient hardener and the formation of the crosslink structure of the paint film obtained is unsatisfactory, and the solvent resistance is reduced. Furthermore, if the (c) component content is less than 5% by weight the solvent resistance is inadequate, and if the amount exceeds 40% by weight then the acid resistance is reduced. Moreover, if the (d) component content is less than 2% by weight then the acid resistance is unsatisfactory, and if the amount exceeds 40% by weight then the paint film obtained is liable to yellowing.
Moreover, the hardened paint films obtained from thermoset paint compositions of this invention must have a glass transition temperature of at least 50xc2x0 C., and preferably of from 55 to 90xc2x0 C., in order to provide the prescribed excellent paint film performance. If the glass transition temperature is less than 50xc2x0 C. then the water repelling properties and the staining resistance are reduced, and this is undesirable.
The paint compositions of this invention can be prepared by compounding the aforementioned components (a) to (d) in the proportions indicated above and mixing in the usual way with the usual means for the mixing of paints. Furthermore, polymers, such as acrylic based polymers, polyester based polymers, urethane based polymers, non-water dispersible type acrylic based polymers and crosslinked polymer particles for example; colorants, such as pigments and dyes; and additives, such as pigment dispersants, anti-run agents, leveling agents, hardening catalysts, gelling inhibitors, ultraviolet absorbers and radical scavengers which have been generally used in paints in the past, can be added, as required, in addition to the aforementioned essential components (a) to (d) within the range where the aim of the invention is not lost.
The paint compositions of this invention can be diluted with organic solvents. The usual paint solvents, such as aromatic solvents, ester based solvents, ketone based solvents and alcohol based solvents for example, can be used for the organic solvent, and no limitation is placed upon the solvent provided that it is a solvent in which the paint composition of this invention can be dissolved and dispersed.
The paint compositions of this present invention are preferably used as top coat paints, and in this case a base coat is painted after applying a primer paint and an undercoat paint, such as an electrodeposition type paint, to the surface of the item which is being painted, and then applying an intermediate paint as required, and then the top coat paint comprising a paint composition of this invention is painted over the top. In this case, the top coat paint may be applied after the base coat paint film had been hardened, but a two-coat one-bake painting system in which the top coat is applied over the base coat paint film in an unhardened or semi-hardened state and hardened at the same time as the base coat paint film is preferred. Furthermore, a one-coat one-bake painting system or an over-coating painting system, for example, can also be employed.
Methods of forming thermoset paint films of a paint composition of this invention include those in which a paint solution obtained by diluting a paint composition of this present invention with the aforementioned organic solvents is painted on by brushing, air spraying, dipping or rolling, for example, or by electrostatic painting, for example, and allowing a setting time of some 5 to 30 minutes and providing a satisfactorily smooth paint film, and then allowing the internal solvent to disperse to a certain extent and then hardening thermally for some 10 to 60 minutes at a temperature usually of from 100 to 180xc2x0 C. so that a hardened paint film is obtained.
Materials which can be painted with a paint composition of this invention include metal surfaces, such as iron, steel, aluminum, zinc and alloys of these metals for example, and sheets which have been subjected to surface treatments, such as iron phosphate treatment, zinc phosphate treatment or chromate treatment for example, plastic surfaces, such as polyurethane, polypropylene and polycarbonate for example, and wood surfaces.
The thermoset paint compositions of this invention are such that the polarity of the main resins and the glass transition temperature of the hardened paint film are controlled, and so the water repelling properties and staining resistance which are the distinguishing features of a fluorine resin based paint film are retained over a prolonged period of time. Furthermore, the hardened paint film is highly abrasion resistant and acid resistant because it has a soft segment structure and urethane bonds which have excellent resistance to chemical attack. Moreover, paint films of which the adhesion properties on recoating are excellent as well are obtained.